1. Field of the Invention
This invention relates in general to flat form gas discharge channel lamps for providing fluorescent or neon light. The various embodiments of the invention have a wide range of application where flat form lamps are desirable such as in computer displays, space lighting, illuminated alpha numeric displays and the like.
2. Description of the Prior Art
In the prior art, gas discharge lamps have been provided for enclosing an ionizable medium in a vacuum-sealed glass envelope which has a thin and flat configuration. In order to withstand the force of atmospheric pressure while keeping the glass thickness relatively thin, one or both sides of the envelope are formed with channels separated by ribs in the manner disclosed in International Application PCT/US91/004997 Thin Configuration Flat Form Vacuum-Sealed Envelope with international filing date of Jul. 19, 1991 by Lynn et al. and which is assigned to the assignee of the present invention.
Among the prior art literature is U.S. Pat. No. 3,646,383 to Jones which provides a fluorescent panel lamp having a series of channels of U-shaped cross-section for containing the ionizable medium. Also, U.S. Pat. No. 3,226,590 to Christy provides another type of fluorescent panel lamp with channels having semicircular cross-sections for containing the ionizable medium. Prior art flat form channel lamps inherently have brightness uniformity problems. That is, the lamp area is not uniformly illuminated because the unraised portions of the front plate forming the channels partially blocks off illumination from the lamp. The prior art attempts to reduce the brightness uniformity problem is exemplified by the Jones patent which provides a specified depth-to-width ratio of the groove between the channels, and control of a nearly vertical groove wall angle, to partially increase the light in the area between the channels. Similarly, the Christy patent controls the wall angle of the channel sides for partially increasing the light in the inter-channel area.
European patent no. 77,077 of Schipp is an example of a lamp having a flat plate on the light output side. The flat plate covers a back side which has a formed shape with mirrored surfaces to create complex reflecting angles. A similar concept is embodied in conventional tubular fluorescent lamps which use reflectors behind and between the lamps to redirect the light forward. However, these designs require adequate space behind the lamps for placement of the reflectors, and are impractical where thin configuration lamps are required, such as for backlighting of LCD screen displays for computers.